Composite double refraction member

Abstract

The present invention provides a composite birefringent member including a first birefringent layer and a second birefringent layer. The second birefringent layer is formed on at least one surface of the first birefringent layer. In the wavelength range from 400 to 800 nm, a value of Δnd x /Δnd 550 and a value of Rth x /Rth 550 of the composite birefringent member as a whole are different from each other. The composite birefringent member satisfies a requirement that the second birefringent layer is formed of a polymer such as polyamide and/or a requirement that Δnd and Rth of the composite birefringent member satisfy formulae (I) and (II) below. As a result, the composite birefringent member allows a liquid crystal display to achieve a wide viewing angle, compensates birefringence of a liquid crystal cell, and does not cause display coloring of the liquid crystal display. Δ nd 400 /Δnd 550 <1   (I) Rth 400 /Rth 550 >1   (II).

1. A composite birefringent member comprising:
 a first birefringent layer; and 
 a second birefringent layer, the second birefringent layer being formed on at least one surface of the first birefringent layer, 
 wherein a value of Δnd x /Δnd 550  and a value of Rth x /Rth 550  of the composite birefringent member as a whole are different from each other in a wavelength range from 400 to 800 nm except 550 nm, and the composite birefringent member satisfies at least one of the following requirements (a) and (b): 
 (a) the second birefringent layer is formed of at least one non-liquid crystal polymer selected from the group consisting of polyamide, polyimide, polyester, polyetherketone, polyaryletherketone, polyamide imide and polyesterimide; and 
 (b) Δnd and Rth of the composite birefringent member satisfy formulae (I) and (II) below,
     Δnd   400   /Δnd   550 <1   (I) 
     Rth   400   /Rth   550 >1   (II) 
 
 and Δnd of the first birefringent layer>Δnd of the second birefringent layer, and Rth of the first birefringent layer<Rth of the second birefringent layer, 
 In the above, 
 Δnd x  and Rth x  respectively represent Δnd and Rth at a wavelength of x nm, 
 Δnd 550  and Rth 550  respectively represent Δnd and Rth at a wavelength of 550 nm, 
 Δnd is (nx−ny)×d, and 
 Rth is (nx−nz)×d, 
 where nx, ny and nz respectively represent refractive indices in an X-axis direction, a Y-axis direction, and a Z-axis direction in the composite birefringent member, the first birefringent layer and the second birefringent layer, with the X-axis direction being an axial direction exhibiting a maximum refractive index within a plane of the composite birefringent member, the Y-axis direction being an axial direction perpendicular to the X axis within the plane, and the Z-axis direction being a thickness direction perpendicular to the X axis and the Y axis, and d represents a thickness of the plane of the composite birefringent member. 
 
     
     
       2. The composite birefringent member according to  claim 1 , wherein only the requirement (a) is satisfied. 
     
     
       3. The composite birefringent member according to  claim 1 , wherein only the requirement (b) is satisfied. 
     
     
       4. The composite birefringent member according to  claim 1 , wherein both the requirements (a) and (b) are satisfied. 
     
     
       5. The composite birefringent member according to  claim 1 , wherein the second birefringent layer is formed of a material that is different from a material for forming the first birefringent layer. 
     
     
       6. A laminated polarizing plate comprising a composite birefringent member, wherein the composite birefringent member is the composite birefringent member according to  claim 1 . 
     
     
       7. A liquid crystal display comprising a liquid crystal cell and an optical member, the optical member being disposed on at least one surface of the liquid crystal cell,
 wherein the optical member is the composite birefringent member according to  claim 1 . 
 
     
     
       8. An image display selected from the group consisting of a liquid crystal display, a plasma display and an electroluminescence display, the image display comprising the composite birefringent member according to  claim 1 . 
     
     
       9. The composite birefringent member according to  claim 1 , wherein the first birefringent layer is formed of at least one material selected from the group consisting of polyethylene, polypropylene, polynorbornene, cellulose-based polymers, polymer carbonate resins, and mixtures of these materials. 
     
     
       10. A liquid crystal display comprising a liquid crystal cell and an optical member, the optical member being disposed on at least one surface of the liquid crystal cell,
 wherein the optical member is the laminated polarizing plate according to  claim 6 . 
 
     
     
       11. An image display selected from the group consisting of a liquid crystal display, a plasma display and an electroluminescence display, the image display comprising the laminated polarizing plate according to  claim 6 . 
     
     
       12. An image display comprising the composite birefringent member according to  claim 1 . 
     
     
       13. An image display comprising the laminated polarizing plate according to  claim 6 . 
     
     
       14. The composite birefringent member according to  claim 1 , wherein Δnd and Rth of the second birefringent layer exhibit wavelength dispersions that are smaller than those of the Δnd and Rth of the first birefringent layer. 
     
     
       15. The composite birefringent member according to  claim 1 , wherein the second birefringent layer and the first birefringent layer are arranged so that their slow axes are orthogonal to each other.